Chemical agent detectors and their method of use for detecting chemical nerve agents

ABSTRACT

There is provided a new and useful paper type G and or type V chemical agent detector comprising a paper base including, associated with the base, at least one dye chosen from 4-((4-(phenylazo)phenyl)azo)-phenol (D.Y. 23), p-ethoxyphenyl-azo-α-hydroxynaphthoic acid (PEN), or 3&#39;, 3&#34;, 5&#39;, 5&#34;-tetrabromophenolphthalein ethyl ester (TBPE).

This is a division of application Ser. No. 07/446,569, filed Dec. 5,1989, now U.S. Pat. No. 5,009,845, which, in turn, is a continuation inpart of Ser. No. 07/263,186, filed Oct. 27, 1988, now abandoned.

This application relates to paper chemical agent detectors.

BACKGROUND OF THE INVENTION

Paper chemical agent detectors for certain chemical warfare purposeswere developed some 20 years ago and have been in widespread use by themilitary of many nations. In their most sophisticated form thesedetectors consist of a paper base in which three dyes have beenincorporated, each dye being sensitive to a particular family of liquidchemical warfare agent droplets. These droplets react with the specificdyes to produce colour changes on the paper. According to the colourchange produced, the type of chemical warfare agent can be identified.

Other forms of paper chemical agent detectors contain only one dye. Inthese cases not as much information on the type of chemical warfareagent can be obtained from the reaction with the paper detector.

A paper chemical agent detector strip is attached to the clothing orequipment of service personnel so that these personnel can immediatelydetermine whether they or their equipment have been exposed to liquidagent contamination. Also, the paper can be used to determine if anunknown liquid on clothing, equipment, or terrain is a chemical warfareagent.

The preferred method of manufacturing these detectors is to include thedyes in the papermaking slurry so that they are integral with the paper.

As currently utilized the detectors incorporate three dyes, one each forthe detection of H-type agents (mustard), G-type nerve agents and V-typenerve agents.

It has come to light that two of the three dyes heretofore incorporatedin the detectors are mutagenic. That being the case, it will be verydifficult or, more likely, no longer possible to utilize these two dyes.It is therefore required that new dyes be sought which meet the variouscriteria which are required to make the detectors.

These criteria include insolubility of the dyes in water during thepapermaking process and solubility in the appropriate chemical warfareagent. The dyes must be solids with a minimum melting point which willkeep them solid during a paper drying process and must give the correctstrong colour on reaction with chemical warfare agent droplets. Thereare various other requirements including compatibility in terms ofcolour produced with other dyes in the detector.

The present invention provides paper chemical agent detectorsincorporating dyes which meet the criteria set out above and which dyesare non-mutagenic.

PRIOR ART

The paper chemical agent detectors in widespread use heretoforeincorporated three dyes as follows: ##STR1##

The non-mutagenic red dye2,5,2',5'-tetramethyltriphenylmethane-4,4'-diazo-bis-hydroxynaphthoicanalide (hereinafter called Red E or simply E) continues to be usableand does not need replacement. Red E is described in the publication E.R. Nestmann et al, Carcinogenesis, Vol. 2(9), 879-883 (1981). Only theyellow dye and the indicator dye, the dyes utilized for the detection ofG-type and V-type nerve agents respectively, need replacement.

BRIEF SUMMARY OF THE INVENTION

It has now been found that the various criteria which must be met by theyellow dye for use in the indicator papers are met by the following twodyes: ##STR2## Chemical Name: 4-((4-(phenylazo)phenyl)azo)-phenol##STR3## Chemical Name: p-ethoxyphenyl-azo-α-hydroxynaphthoic acid.

The first of these, which is sold under the common name Disperse Yellow23 (C.I. 26070), will hereinafter be referred to as D.Y. 23; and thesecond will hereinafter be designated as PEN.

A suitable replacement for the indicator dye meeting all of thenecessary criteria is the following: ##STR4## Chemical Name:3',3",5',5"-tetrabromophenolphthalein ethyl ester.

This last dye is hereinafter referred to as TBPE.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The desired dye for the detection of G-type nerve agents is a yellowdye; that is a dye which assumes a strong yellow colour when dissolvedin liquid G-type nerve agents. The background colour of the paper isnormally a beige, and the yellow must clearly contrast this background.Usually, especially with larger droplets, the yellow colour has anorange tinge to it. As indicated above, the dye must be insoluble inwater but must be soluble in G-type nerve agents which have the generalformula ##STR5## wherein for GD agents, R¹ is CH₃ and R² isCH(CH₃)C(CH₃)₃ and for GB agents, R¹ is CH₃ and R² is CH(CH₃)₂.

It is also highly desirable that the dye be insoluble in such liquids aspetroleum products, antifreeze solutions and alcohol solutions which arelikely to be encountered in battlefield conditions.

As indicated above, the dye must remain solid during any dryingprocesses including the papermaking drying step and should thereforehave a melting point greater than 100° C. It must furthermore besufficiently stable to give the detector a good shelf life.

The dye must be non-mutagenic.

After extensive testing two dyes were found which met all of thesecriteria. These comprised D.Y. 23 and PEN. Having met the generalcriteria relating to melting point, water solubility, response to agentsand compatibility with other dyes in handsheets, additional testing wasundertaken to establish appropriate loading and particle size forincorporation into paper and to test sensitivity of the paper to smallnerve agent droplets.

Tables I and II below set out the test results for D.Y. 23 and PENrespectively.

                  TABLE I                                                         ______________________________________                                                                          G-NERVE                                             DYE          BACKGROUND   AGENT                                       DYE(S)  LOADING (%)  COLOUR       RESPONSE                                    ______________________________________                                        D.Y. 23 0.2          white        light                                                                         yellow                                      D.Y. 23 0.4          white        yellow                                      D.Y. 23 0.6          off-white    yellow                                      D.Y. 23 0.8          v. light     yellow                                                           brown                                                    ______________________________________                                    

In respect of D.Y. 23, the dye was ground through a No. 250 mesh screen,and handsheets were loaded with dye loadings ranging from 0.2 to 0.8percent (dye loading is defined as parts by weight dye per 100 parts byweight dye plus dry pulp). As can be seen from Table I, handsheets withD.Y. 23 loadings as low as 0.4 to 0.6 percent gave the required yellowresponses when tested with 100 to 110 micrometer droplets of GD. Theseresults not only satisfy the criteria discussed above, but show markedimprovement over the yellow dye being replaced.

                  TABLE II                                                        ______________________________________                                                                          G-NERVE                                             DYE          BACKGROUND   AGENT                                       DYE(S)  LOADING (%)  COLOUR       RESPONSE                                    ______________________________________                                        PEN     0.1          light tan    N/R                                         PEN     0.2          light tan    N/R                                         PEN     0.3          light tan    N/R                                         PEN     0.5          light        v. light                                                         brown        yellow                                      PEN     0.6          light        v. light                                                         brown        yellow                                      PEN     0.8          light        light                                                            brown        yellow                                      PEN     1.0          light        light                                                            brown        yellow                                      PEN     1.2          light        light                                                            brown        yellow                                      ______________________________________                                    

With respect to PEN, the dye was screened through a No. 230 mesh screenand incorporated into handsheets with loadings ranging from 0.1 to 1.2percent. The sheets were tested with 100 to 110 micrometer droplets ofliquid GD. These tests indicated that PEN gave a light yellow responseat dye loadings above about 0.8 percent. Note that these were very smalldroplets and that much stronger yellow colours would be obtained withthe larger more normal droplets.

Turning to the required replacement for the third dye, being anindicator dye, the criteria are generally the same as those in respectof the yellow dye but with some variation. The dye must change colour toa very dark green or preferably to dark blue in the presence of a base.The colour change must take place at a low enough pH for the dye toreact with V-type nerve agents (which contain a substituted amine group)but this pH must be high enough to be compatible with papermakingprocedures. The approximate permissible range is pH 3.5 to 8. The dyemust be insoluble in water at papermaking pH levels and must be solublein V-type nerve agents.

Other of the criteria are shared with the other dyes. It must remainsolid during drying procedures, must be stable enough to provide a goodshelf life to the detectors and must be non-mutagenic.

After extensive testing it was discovered that TBPE satisfied all of theabove criteria. Utilizing the preferred known dye loading for the reddye and the preferred dye loadings as determined above for D.Y. 23 andPEN, handsheets were prepared to test various dye loadings of TBPEincorporated into sheets also containing red dye and either D.Y. 23 orPEN. The results of this testing are summarized in Table III.

                  TABLE III                                                       ______________________________________                                                DYE                      VX-NERVE                                             LOADING    BACKGROUND    AGENT                                        DYE(S)  (%)        COLOUR        RESPONSE                                     ______________________________________                                        E       0.75       greenish      red                                          D.Y. 23 0.6        grey          yellow                                       TBPE    1.2                      v. dark green                                E       0.75       grey          red                                          D.Y. 23 0.6                      yellow                                       TBPE    1.0                      v. dark green                                E       0.75       light         red                                          D.Y. 23 0.6        grey          yellow                                       TBPE    0.8                      dark green                                   E       0.75       light         red                                          D.Y. 23 0.6        grey          yellow                                       TBPE    0.6                      green                                        E       0.75       light         red                                          D.Y. 23 0.6        grey          yellow                                       TBPE    0.4                      light green                                  E       0.75       light         red                                          D.Y. 23 0.6        grey          yellow                                       TBPE    0.2                      yellow                                       E       0.75       light brown   red                                          PEN     1.2                      v. light yellow                              TBPE    0.8                      green                                        E       0.75       brown         red                                          PEN     1.2                      light yellow                                 TBPE    1.0                      green                                        E       0.75       brown         red                                          PEN     1.2                      light yellow                                 TBPE    1.2                      dark green                                   ______________________________________                                    

The results summarized in Table III indicate that the blue indicator dyeTBPE is capable of detecting 100 to 110 micrometer droplets of the nerveagent VX but that the loading should preferably be at least 0.8 percentor more preferably 1.0 or 1.2 percent in order to give the required darkgreen response. It should be noted that TBPE actually gives a dark bluecolour with VX but, since VX also disolves the yellow dye, theirresultant colour response is dark green.

In respect of all three dyes, dye loadings up to about 2.0% might beutilized. Above that amount the detector becomes too expensive and inany event there is no significant improvement in detecting ability.

The paper base into which the dyes are incorporated can vary over a widerange of constituents. A preferred formulation comprises, in addition toa basic pulp formulation, agents for improvement of wet and drystrength, for pH control, for water repellency and for binding purposes.A typical formulation may contain a melamine-formaldehyde resin toimprove wet and dry strength, and anionic emulsion of a sizing agent toimpart water repellency, sodium aluminate for pH control and provisionof aluminum ions, and alum for the provision of aluminum ions, thealuminum ions interacting with pulp fibres to bind the sizing agent tothe fibres.

A typical melamine-formaldehyde resin is Parez 607™. A suitable sizingagent is Newphor 100™.

The order of addition of the additives to the pulp slurry is importantand comprises in order the resin, the aluminum/sodium aluminate, thesizing agent and the dye slurries.

While the concentrations of the various additives may be varied oversubstantial ranges to suit particular conditions, a typical andpreferred formulation comprises a pulp slurry comprising a 50:50 mixtureof softwood and hardwood pulp, and containing on a parts of additive per100 parts slurry basis Parez 607 3.0, alum 2.1, sodium aluminate 0.3 andNewphor 100 0.5. Typical particle sizes for the dyes included in thepreferred paper slurry formulation are as follows. For the red dye awater slurry crushed in a roller mill at a 0.5 millimeter gap followedby filtering the slurry through a No. 200 mesh screen is suitable. Asimilar procedure is suitable for D.Y. 23. The TBPE and PEN arepreferably passed dry through a No. 230 mesh screen and then dispersedin acidic water. Other particle sizes may be used, but if the particlesize becomes too small, the paper will develop unacceptable backgroundcolour; and if the particle size becomes too large, the paper will notbe capable of detecting very small droplets of chemical warfare agents.

A typical pH for the pulp formulation is about 4.2.

It will be appreciated by those skilled in the art that the detectordyes according to the invention are not novel compounds per se. Forexample, as indicated above, Disperse Yellow 23 is a well documented dyematerial. PEN is described in the publication A. C. Sircar et al, J.Soc. Chem. Ind., Vol. 31, 968 (1912) and TBPE is described in thepublication M. M. Danis et al, J. Research Nat'l, Bur. Standards, Vol.39, 221 (1947). However, the use of such materials for detecting and/oridentifying chemical agents is both new and unobvious. Moreover,although it is preferred according to the invention that the detectordyes are associated with a base or substrate such as paper and varioussuitable fabric materials, it is contemplated that the detector dyescould also be used without such a base or substrate under theappropriate conditions as would be apparent to those skilled in the art.

We claim:
 1. A method of detecting type G chemical nerve agentscomprising exposing a detector material to a fluid, said materialcomprising at least one dye selected from the group consistingof4-[(phenylazo)phenyl)azo]-phenol (Disperse Yellow 23), andp-ethoxyphenyl-azo-α-hydroxynaphthoic acid (PEN), and examining thedetector for a predetermined color change in the detector confirming thepresence of said chemical agent.
 2. The method of claim 1, wherein thedetector material comprises4-[(phenylazo)phenyl)azo]-phenol (DisperseYellow 23), whereby in the presence of a G-type chemical agent thedetector material assumes a characteristic yellow color.
 3. The methodof claim 2, wherein the detector material is impregnated in a papersubstrate.
 4. The method of claim 1, wherein the detector materialcomprisesp-ethoxyphenyl-azo-α-hydroxynaphthoic acid (PEN), whereby inthe presence of a G-type chemical agent the detector material assumes acharacteristic yellow color.
 5. The method of claim 4, wherein thedetector material is impregnated in a paper substrate.
 6. A method ofdetecting a V-type chemical agent, comprising exposing a detectormaterial to a fluid, said detector material comprising3',3",5',5"-tetrabromophenolphtalein ethyl ester (TBPE), whereby in thepresence of a V-type chemical agent the detector material assumes acharacteristic green color.
 7. The method of claim 6, wherein thedetector material is impregnated in a paper substrate.